Question

Answer the following question :
What is the difference between calcination and roasting.

Answer 1

Calcination	Roasting
1. The ore is heated in the absence of air	1. The ore is heated in excess of air.
2. Moisture and organic impurities are removed, and the ore becomes porous and more reactive.	2. Volatile impurities are removed as oxides (SO2, P2O5, As2O3), and the ore becomes porous and more reactive.
3. Carbonate and hydrated ores are calcined, and CO2 or water vapour is given off. ZnCO3 → ZnO + CO2	3. Sulphide ores are roasted, so SO2 is given off. \[\ce{2ZnS + 3O2 ->[80°-90°] 2ZnO + 2S}\]